1. Field of the Invention
The present invention relates to an apparatus for damping the swing of a loading device, said apparatus comprising a trolley provided with a hoisting machine, operating a hoisting rope on which a loading device is suspended, and downward-pointing brackets attached to the bottom of the trolley.
2. Description of the Related Prior Art
The swing of the loading device of a crane can be damped by using an even driving speed, avoiding jerks and large changes of speed, and the operator may hold the load steady while operating the crane However, these expedients are generally only applicable in the case of small loads In the hoisting of heavy and large loads, the damping systems mentioned below are used.
To damp the load swing, cranes generally employ systems where the load is lifted into a position between the brackets attached to the bottom of the trolley The loading device consists of several bars or it may have a structure resembling a funnel, a box, etc.
This type of damping system has the drawback that when the loading device is hoisted at a high speed into the position between the brackets, the gap between the device and the brackets must be sufficiently wide, which in turn leads to after-swing. A narrow gap between the loading device and the brackets produces large lateral forces as the loading device may hit the brackets, in which case the load may fall from the loading device. The above-described problem has been solved employing known techniques, whereby four brackets are placed symmetrically around a cylindrical loading device so that a suitable gap is left between the brackets and the loading device. Using a pneumatic device, damping elements designed to lock the loading device in place between the brackets are installed in this gap. Besides being complex, such a system is also very expensive and restricts the hoisting speed of the load.
The swing of the loading device can also be damped using a system based on telescopic or scissor guidance. Such systems allow the damping of the swing caused by the turning or lifting the load. These damping systems are expensive and require plenty of material and space.